Speed regulator



Nov. 11, 1941.

F. H. GULLIKSE'N SPEED REGULATOR Filed Sept. 7, 1939 VWa;

INVENTOR ATTORNEY Patented Novo 11, 1941 v SPEED REGULATOR Finn H. Gulliksen, Pittsburgh. PL, alslgnor Westinghouse Electric & Manufacturing Compony, East Pittsburgh, Pa a corporation of Pennsylvania Application September 7, 1939, Serial No. 293,728

iClaims.

My invention relates to electronic speed resulators and is particularly adapted for regulating the speed of an electric motor in a manner to cause it to follow the speed of a master motor or speed reference device.

In industrial applications where a plurality of separate section driving motors are employed for driving the individual sections of a machine and it is desired to maintain a predetermined speed relation therebetween, sectional speed regulator systems have been employed for controlling the speeds of the several section driving motors with respect to the speed of a master motor. It is customary in such regulator systems to employ a mechanical differential device that is responsive both to the speed of the regulated motor and to the speed of the master motor for developing a control impulse that varies in response to the difl'erential relationship between these two revolving members. Such devices usually take the form of mechanical differential mechanisms which are not practical when electronic regulators are employed because such devices are relatively large and expensive parts of the ap aratus.

It is an object of my .1. vention to provide an electronic speed regulator system for electric motors in which the corrective impulse is established by varying the rate of flow of unidirectional current in a detector circuit.

It is a further object of the invention to provide means differentially responsive to a master speed reference means and to the speed of the regulated motor that is simple in operation, inexpensive to manufacture, and that is quickly sensitive to variations in the speed of the regulated motor from its desired value.

Other objects and advantages of the invention will be apparent from the following description of a preferred embodiment thereof, reference being made to the accompanying drawing, in which Figure l is a schematic diagram of circuits and apparatus employed in one embodiment of the invention;

Figs. 2 and 3 are detailed views of parts of the apparatus shown in Fig. l; and

Figs. 4 and 5 are curves illustrating the operation of the equipment.

Referring particularlyto Fig. 1 of the drawing, a motor I is illustrated which is operative to drive a shaft 2 at a speed that is a measnre of the desired speed of operation of a regulated nectpd through gearing i2 torotate in accordance with the speed of the. master motor I. A disc II is provided at the upper end of the housing 1 and, as best shown in Fig. 3, is provided with a circumferential slot H of varying width from a maximum value at it to a minimum value at it. The housing ll carries a disc ll at its upp r end, which is provided with a narrow slot II that extends outward radially from the axis of rotation of the disc, as best shown in Fig. 2. The relative positions of the discs winding 20, the excitation of which controls the motor speed. The field winding is supplied with energy from a full-wave rectifier comprising grid controlled tubes 21 and II. The tubes 21 and N are provided with anodes 3| and 3!, respectively, and with cathodes l3 and II, respectively, the anodes being connected to the opposite ends of a secondary winding 35 of a transformer having a primary winding 3!. The field winding circult extends from the midpoint of the winding 3| through conductor 31, field winding 20, conductor ll, through the tubes 11 and 2! to the transformer winding 3!. The tubes 21 and 2! are also provided with control grids II and 41, respectively, that are connected to the opposite terminals of the secondary winding 43 of a grid transformer II. The grid-control circuit extends from the center point of the winding ll through conductor 4!, a condenser u, resistors 41 and 48 and conductor 0 to the cathodes 33 and N of tubes 11 and II, respectively. The grid transformer 44 is provided with a primary winding II that is connected by conductors 82 and Bl to a well known type of phase shift circuit comprising the secondary transformer winding It, a resistor II, and condenser 55 for applying a voltage to the grid circuit that is out of phase with the voltage applied between the anodes and cathodesof the tubes 21 and 28.

The potential across the condenser 43 is determined by the output voltage of the full-wave rectifier Bl which may be of the dry or copperoxide type, the alternating current terminals of which are connected to be supplied with energy from the secondary winding I! of a transformer II. The primary winding 8. of the transformer 58 is supplied from the secondary winding 6! and is connected in series with a load device, such as the rectifier 62, here shown as a fullwave rectifier of the dry or copper-oxide type. The output or direct current terminals oi! the rectifier 62 are connected to the anode 63 and cathode 6d of a tube 85, the conductivity of which is'determined by the control grid 66. The control circuit for the grid 66 extends from the cathode 64 through conductors 61 and 23, reslstor 24 and conductors 86 and 58 to the grid 66. The voltage drop across the resistors 4! and 48 are determined by operation of grid controlled tubes !l and 12 provided with anodes l3 and 14, respectively, cathodes 15 and 16, respectively, and control grids l1 and 18, respectively. A direct current supply of energy. represented by conductors 8| and 82, is provided between which conductors a resistor 83 is shown connected, and to some intermediate point 85 thereon the cathodes 15 and 16 are connected to give the desired voltage drop across the tube terminals. The control grids l1 and 18 are connected by conductors 86 and 81, respectively, to the opposite ends of a resistor 88, one end of which is connected to one end of the resistor 24 by the conductor 86 and the opposite ends of which are connected together through a condenser 89 so that changes in the voltage across the resistor 88 follows that across the resistor 24 but with a time lag. The direction of voltage drop across certain of the various parts of the circuits are shown in Fig. 1 of the drawing.

Referring to the operation of the system disclosed, it will be apparent that the regulator is essentially a "phase angle regulator in which the energization of the field winding 26 of the motor 3 is varied in accordance with a change in the phase angle position between the shafts 2 and 4 which'eilect a corresponding change in the phase angle relationship between the discs i1 and [Son the two housings H and I, and consequently a change in the intensity of the illumination that impinges on the phototube 2|.

It is obvious that a variable amount of light is permitted to impinge on the phototube 2| depending upon the relative positions of the shafts 2 and. 4. If the discs l3 and H are in the relative positions shown in Figs. 3 and 2, the 11- lumination on the phototube will be low. If the disc l3is turned clockwise relative to the disc H, the illumination on the phototube increases as the width of the slot l4 increases from the narrow value shown at I6 to a greater width de pending upon the degree of movement of the disc l3 until it has moved through approximately 360. If the system is so arranged that normal motor speed results from a displacement of the disc l3 through 180 from its illustrated position in Fig. 3 so that an intermediate width of the slot I4 is adjacent the slot IS on the disc I], then a change in the position of the disc I3 in the one or the other direction from this position will correspondingly vary the intensity of iilumination on the tube 2| in the one or the other positions.

It the two discs l3 and ii are in the 180 position and the speed of the motor 3 increases slightly above its desired speed, the disc i3 will move in a clockwise direction with respect to the disc ll, thus increasing the illumination on the phototube 25. This increase in illumination on the phototube 2i causes an increased current flow from the battery 22 through the resistor 2 thus causing thc grid of the tube 65 to become more negative so that less current flows through the tube 65. Consequently, the load on the rectifier i2 is decreased, and the voltage drop thereacross correspondingly decreased, so that the voltage across the winding 59 is increased more nearly to the voltage of the secondary winding 6!. This increase in voltage is reflected in the secondary winding 51 to apply a greater voltage to the rectifier 55 applied across the condenser 46, thus making thecontrol grids 4i and 42 more positive and increasing the flow of current in the field winding 26 to decrease the motor speed. Should the speed of the motor 3 decrease with respect to that of the motor I, the phase angle relation between the discs l3 and I] would vary in the opposite direction, thus dacreasing the illumination on the phototube 2| and producing the reverse result in the circuits just describedythus decreasing the current supplied to the field winding 26 and increasing the motor speed.

In the description of the control circuits for effecting variations in the excitation of the field winding 26 thus. far described, it has been assumed thatthe potential drop across the re sistors 41 and 48 will not appreciably affect the grid potentials of the tubes 21 and 28. This will be true providing the rate of change in phase angle between the discs l3 and I1 takes place slowlyand they are in the intermediate portion of the operating range of the equipment. It will be noted that when the disc i3 moves in a clockwise direction with respect to the disc H, the illumination varies substantially along the curve shown in Fig. 4, that is, gradually increases over a portion 8| until the 360 position is Ill reached when the illumination drops suddenly, as shown by the portion of the curve 82. If the speed of the motor 3"*-decreases, the disc [3 will move in a counterclockwise direction with respect to the disc I! so that the illumination will vary in accordance with the curve shown in Fig. 5, that is, it will decrease gradually over the 360 as shown by the portion of the curve 93 and increase suddenly, as shown at 94. If the phase angle relation between the discs I! and I1 varies past the 360 position so as to efiect an abrupt change in the illumination of the tube 2|, as shown by the portions 92 and 94 of the curves in Figs. 4 and 5, respectively, the effect of the change in illumination on that portion of the control circuit, including the tube 65- and rectifiers 62 and 55, will reverse the direction of correction, which is undesirable. This condition is reached, for example, while the motor is being brought up to speed under which condition it is desirable to maintain a weak held on the motor regardless of the relative position of the discs I! and I3 until the desired speed is reached and the relative motion between the discs becomes gradual.

In the regulator system described, circuits are provided for diiferentiating between changes in illumination occasioned by passing the 360 relation between the two discs and a change in illumination that is occasioned by a reversal in the direction oi one disc with respect to the other. It the motor suddenly increases its speed so that the displacement between the discs l3 and H exceeds the 360 position, the illumination on the phototube 2| decreases abruptly substantially to zero value, causing a decrease in the current flow from the battery 22 through the resistor 24. This causes the condenser 89 to discharge through the local circuit including resistors 88 and 24 providing a large voltage across the resistor 88 with the polarity indicated in Fig. 1. This causes a large increase in the potential of the grid 18 of tube 12 with respect to the cathode 18 by adding a large positive voltage component in the grid control circuit which grid circuit extends from the cathode 16 through conductor 95, the lower portion of the resistor 83, conductor 96, the righthand portion of resistor 88, and conductor 81. At the same time, a negative voltage component is introduced into the grid control circuit of the tube 1i which grid control circuit extends from the cathode 15, through conductor 95, the lower portion of the resistor 84, conductor 96, through the left portion of resistor 88 and conductor 86 to the grid 11 causing the tube 1| to become non-conducting. When the tube 12 becomes conductive. current flows therethrough charging the condenser 81 that is connected in parallel with the resistor 48 to a higher than normal'value. At the same time, the normal charge on the condenser 98 connected in shunt to the resistor 41 is discharged through the resistor 41. The effect of the increasing charge on the condenser 81 and the decreasing charge on the condenser 88 results in differentially varying the voltage drop across the resistors 48 and 41 with a polarity in a direction to make the grids of the tubes 21 and 28 more positive, thus increasing the current through the field winding 26 to continue to decrease the mtor speed. It is desirable that the circuit constants be so chosen that the voltage obtained from control circuit, and means for oppositely varying the values of said two voltage components in accordance with the rate of change of said control potential.

2. In a regulator system, an electric motor, a

master speed reference means operated at a speed I that is a measure of the desired speed of the regu lated quantity. a source of light and a light controlling mechanism comprising a pair of discs having apertures therein for varying the intensity of a beam of light therethrough from said source upon variations in the relative positions of said pair of discs, means for driving said two discs in the same direction at speeds corresponding, respectively, to the speeds of the motor and of the speed reference means, means responsive to the intensity of said beam of light for establishing a control potential, an electronic rectifier for supplying energy tothe field winding of said motor,

a grid control circuit therefor including a grid transformer, and means for introducing, a unithe resistors "and 48 predominate over the voltage component applied, across the condenser 48 from the rectifier 58.

It will be apparent that it the motor speed decreases and the disc I3 passes through the 360 point, the opposite result will beeflected, that is, the tube 1| will become more conductive and the tube 12 will become non-conductive so that a differential voltage across the resistors 41 and 48 in the grid controlled circuit of the tubes 21 and 28 will result in a differential polarity of opposite efiect. The time constant of the circuits involving resistor 41 and condenser 88, and resistor 48 and condenser 91, should be so chosen that the voltage drop across the resistors 41 and 48 prodominates the voltage across the condenser. during at least 180 relative motion of the two discs I3 and I1.

It will be apparent to those skilled in the art that modifications in the circuits and apparatus described may be made within the spirit of my invention and I do not wish to be limited otherwise than by the scope of the appended claims.

I claim as my invention:

1. In a regulator system, an electric motor, a

master speed reference means operated at a speed that is a measure of the desired speed of the regulated quantity, a source of light, control mechanism having two relatively movable members the relative positions of which determine the intensity of a beam of light from said source, means responsive to the intensity of said beam of light for establishing a control potential, an electronic rectifier for supplying energy to the field winding of said motor, a grid control circuit therefor including a grid transformer and means for introducing a unidirectional potential into said grid control circuit that is a measure of said control potential, means for introducing two voltage components of opposite polarity into said grid directional potential into said grid control circuit that is a measure of said control potential, means for introducing two voltage components of opposite polarity into said grid control circuit, and

means for oppositely varying the values of said two voltage components in accordance with the rate of change of said control potential.

3. In a regulator system, an electric motor, a master speed reference means operated at a speed that is a measure of the desired speed of the regulated quantity, a source of light, control mechanism having two relatively movable members the relative positions of which determine the intensltyof-"a beam of light from said source, means responsive to the intensity of said beam of light for establishing a control potential, an electronic rectifier for supplying energy to the field winding of said motor, a grid control circuit therefor in..

cluding a grid transformer and means for lntroducing a unidirectional potential into said grid control circuit that is a measure of said control potential, two means for introducing voltage components having opposite polarity into said grid control circuit, and means i'or selecting the one or the other of said two means in accordance with the direction of change of said control potential.

4. In a regulator system, an electric motor, a master speed reference means operated at a speed that is a measure of the desired speed of the regulated quantity, a source of light, control mechanism having two relatively movable members the relative positions of which determine the 1 intensity of a beam' of light from said source, means responsive to the intensity of said beam of light for establishing a control potential, an electronic rectifier for supplying energy to the field winding of said motor, a grid control circuit therefor including a grid transformer and means for introducing aunidirectional potential into said grid control circuit that is a measure of said control potential, two grid-controlled means for 

